


A Potion Mishap Gone....Right?

by Aria_Lerendeair



Series: Aria's SH Bingo Fics 2019-2020 [23]
Category: Shadowhunters (TV), The Shadowhunter Chronicles - All Media Types, The Shadowhunter Chronicles - Cassandra Clare
Genre: Alec has temporary tentacles, Alec's tentacles are handsy, Anal Sex, Biting, Blowjobs, Enthusiastically consensual tentacle sex, M/M, Marking, Porn Without Plot, Potion mishaps, Tentacle Sex, Tentacles, This was a very shallow excuse to write tentacle porn, dirty talking, handjobs
Language: English
Status: Completed
Published: 2020-04-26
Updated: 2020-04-26
Packaged: 2021-03-02 09:07:11
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 5,878
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23848678
Author URL: https://archiveofourown.org/users/Aria_Lerendeair/pseuds/Aria_Lerendeair
Summary: A potion leaves Alec with a few extra... appendages.They like Magnus, almost as much as Alec does.
Relationships: Magnus Bane/Alec Lightwood
Series: Aria's SH Bingo Fics 2019-2020 [23]
Series URL: https://archiveofourown.org/series/1595839
Comments: 18
Kudos: 288





	A Potion Mishap Gone....Right?

**Author's Note:**

> Written for the Bingo Fill: Potions Gone Wrong! ....also known as tentacle porn! 
> 
> It's so funny that this is the last prompt for my first bingo card because I knew, the SECOND I saw this square, that it was gonna be tentacle porn.

Alec loved watching Magnus work, especially when it meant that all of his attention was narrowed down to what was happening in front of him. He'd gotten off early from patrol and that meant that he was going to get to spend the entire evening, and even some of the morning with Magnus. He breathed out slow, relaxing, watching as Magnus swayed across the room and grabbed another ingredient flask. 

Bringing it to the potion on the desk that was... 

Alec narrowed his eyes and watched as Magnus' widened in alarm and Magnus waved a hand, just in time for the potion to emit a cloud of dark blue, acrid smelling smoke. 

"Shit!" Magnus swore, his eyes widening. "Too much fairy wing," he cursed again and watched the smoke billow into a larger cloud. He looked around his office. He had to get the smoke out of his office or he was risking some serious cross-contamination. Focusing and pulling on his magic, he exhaled hard, blowing magic towards the smoke cloud, before shaping it and throwing it into the main loft, and right into his boyfriend, standing in the doorway of his apothecary. 

Magnus had one, panicked second to catch Alexander's eyes before the shadowhunter was enveloped in the blue smoke. 

"Fuck!" 

Alec had taken a precautionary step back as soon as he'd seen the smoke, but then Magnus had blown the smoke _at_ him, and he hadn't been able to dive out of the way in time. It clung to him and he clenched his eyes and mouth shut, slapped his hands over his ears and pressed his nose into his arm as deep as he dared holding his breath. The smoke, whatever it was, was landing on him, almost coating him like it was liquid rather than some sort of gas. 

"Alexander!" Magnus shouted, waving his hands again, magic springing to his fingertips easily as he worked to dissipate the gas. Eventually, _finally,_ it started to fade and he sagged in relief at the sight of his shadowhunter still standing, in the best precautionary stance he could have expected with no warning. 

"Alec if you can hear me, don't move," Magnus instructed, reaching out to run his magic over Alec, assessing the substance that he was covered in. When he got the minutest nod in response, he relaxed. "You can breathe through your mouth - no more gas," he added, watching Alec suck in a quick breath of air. 

At the very least, the magic, and the potion didn't seem to be lethal. He sagged in relief. Looked like all it might have done is cause a mess. "Okay. Move, carefully. I need you to tell me if anything feels wrong." 

Alec carefully unwound himself and looked down at Magnus, looking down at the blue tinge of his skin and guessed that the same was on his face. "Uh, nothing feels wrong? It's a bit...tingly where it's on my skin?" 

"Okay, let's get that off you first then," Magnus said with a deep breath, focusing his magic on Alec's face, using it to clean whatever the substance had become off of him. "I'm sorry for blowing it right at you." 

"Well, I wasn't expecting you to do that, but I didn't tell you I was home," Alec said, lifting his head a little to smile at Magnus. When he felt some of the liquid slide down the back of his shirt, he squirmed. "Uh, Magnus?" 

Magnus' eyes immediate sharpened and he watched Alec's whole body flex and then shudder. "Alec? Alexander, tell me what it feels like right now." 

Alec's eyes went wide and he opened his mouth, but it felt like the liquid that was spreading on his back was hot, burning his skin. "Back, burns," he managed to gasp out, falling to his knees. 

Magnus immediately drew all of the power he dared and stripped the rest of the substance off of Alec, and banished his shirt, striding around him in two steps. "Don't worry, don't worry darling, I'll take care of it," he promised, leaning in to get a better look with his magic. 

Anywhere the liquid had touched on Alec's back was slowly turning an iridescent blue and revealing something that looked almost like scales. Magnus sucked in a breath and banished the rest of the excess on Alec's back. "Does it still hurt?" 

"Uncomfortable," Alec grit out, flexing his arms as he tried to hold himself still. "Pressure." He sucked in a hard breath, trying to breathe through it, but it felt like he was being suffocated. "Magnus, fuck, _help."_

Magnus tried to ignore that and focused on the wild magic that had now embedded itself into Alec's back. What could the potion be interacting with that it wouldn't have on Alec's face or hands? He reached out and pressed his fingertips to the magic and was immediately thrown backwards by a limb slamming into him, tossing him across the loft and to the couch. His eyes widened at the sight, right as Alec collapsed to the floor in a heap. 

~!~ 

When Alec woke again, the pressure was gone, and he was curled up in Magnus' arms. He smiled and opened his eyes, humming when Magnus' fingers tightened briefly in his hair. "Mmm, Magnus." 

Magnus let out a relieved exhale, smiling down at Alexander. "There you are. How are you feeling?" 

"Good," Alec managed, shifting a little. He frowned. His back felt heavier than usual. "Uh, what happened?" 

"Before I answer that," Magnus said, glancing up and along the tentacle curling possessively around his lower leg. "Know that they are temporary, and they'll be gone in about a day in a half, and I've already let Isabelle know to take over your duties for that time." 

Alec blinked and stared at Magnus, frowning and titling his head. "I'm sorry, they?" 

"Right," Magnus said, clearing his throat. "You need to sit up, and I'm sure they'll make themselves known. I'm curious if you can feel them." 

Alec sat up slowly, pushing himself upright with a grunt, only to suddenly have his weight supported elsewhere immediately. His arms were hovering off the bed and he was supported by... 

He looked to the side, and there were two blue tentacles on either side of his arms, supporting him. He blinked and looked over his shoulder. Two more immediately made themselves apparent and then he could feel the one that was wrapped around Magnus' leg and the other tucked under their golden sheets. 

"Alexander?" Magnus asked, studying the expression on his boyfriend's face. Alec didn't look upset or scared, only bewildered. "Are you all right?" 

"Magnus," Alec started, fighting to keep himself calm. "Do I have tentacles?" 

Magnus coughed and glanced at the tentacles and then back to Alec's face. "Temporarily, yes. Yes you do." 

"Right," Alec said with another deep breath. He finished getting himself upright and looked down at Magnus, kneeling in the middle of the bed. "This might now top my weirdness scale." 

Magnus snorted. "I'm glad that you're taking this so calmly." The tentacle wrapped around his leg started to creep up the pants he was wearing and he gave it a brief swat. "Stop that!" 

"Ow!" Alec protested, and then blinked, looking down at the extra limb. "Okay, I felt that, and that was _weird."_

Magnus laughed and shook his head, even as another tentacle started to wrap around his waist. "They are a bit...uh...handsy?" he offered, giving one of the tentacles a pat. 

Alec looked down at them, the way all of them seemed to be touching Magnus in some way and he smiled faintly. "That might...be because of me?" He rubbed the back of his head when Magnus looked up at him with raised eyebrows. "What, I always want to be touching you." 

Magnus rolled his eyes and sat up as well, reaching out to pull Alec into a kiss. "I'm sorry about this. They don't hurt?" 

Alec shook his head and rolled his shoulders. "They feel a bit heavy, but nothing I can't handle. Should maybe activate my strength rune to make sure-" 

"No," Magnus said, shaking his head. "I don't know how their magic will mix with runic magic, and right now we know they're going to go away in a day." He gave one of the tentacles a consolation pat when it sagged along his thigh. 

"All right," Alec said, looking at the tentacles and Magnus in front of him, raising his eyebrows. 

He twisted when one of the tentacles started to tug at the waistband of the boxers he was wearing. "Hey," he protested, flushing. "Not right now." A soft gasp had him turning with an eyebrow, because he recognized that gasp. 

One of the tentacles had dropped to Magnus' lap and was rubbing slowly against his cock. Alec watched Magnus' head tip back and his mouth fall open the smallest amount. Now that he was focusing on it, he could feel it and he moved the tentacle, rubbing the tip of it along the tip of Magnus' cock. 

"Fuck," Magnus breathed, trembling a little under the touch. "Is that you or them?" 

"Bit of both?" Alec offered, captivated by the sight, at how Magnus was spreading his legs, just enough so he could roll his hips up easier into the touch. "You like this?" 

Magnus bit down on his lower lip and nodded, meeting Alec's eyes with his glamour down. "Don't judge me too harshly for it?" 

Alec shook his head and used two of the tentacles to give Magnus a push back down on the bed. Now that he was more focused, it was much easier to control them. Two of them were carefully curled into Magnus' hands, pinning them down to the bed and Alec grinned when Magnus' wide eyes met his. "Okay?" he asked. 

Magnus groaned, nodding again. "Are, are you going to...?" 

"If you want me to," Alec breathed. "I want, I want to see how much you like them." 

Shuddering hard, Magnus forced himself to meet Alec's eyes. "Yes, fuck, please. They've been teasing me while you've been asleep and-" 

"Oh have they?" Alec asked, shifting so he was leaning down and over Magnus. "Tell me what they were doing?" he whispered, stealing a quick kiss before sucking a mark into Magnus' neck. 

"Mostly," Magnus panted, whining when he felt a tentacle creep around his hip, making him groan. "Mostly what they're doing right now. Squeezing my ass, teasing me through these sleep pants, wrapping around my arms or legs to hold me close." 

Alec chuckled and pressed a kiss to the mark he'd left, lifting his eyes to look at Magnus. "So pretty much exactly like me when I sleep with you, except if I had six arms?" 

"Something like that," Magnus said, panting as the tentacles pulled harder at his sleep pants. "Was definitely giving me a lot to imagine and think about, but I was considerably more worried about you and making sure you were all right." 

"And now that you know I'm all right?" Alec asked, sliding the tentacle along the curve of Magnus' ass, teasing at his balls and just behind them, watching his boyfriend arch and bite down on his lip. "And maybe very interested in seeing just how much you enjoy this?" 

"Alexander," Magnus growled, only to find a tentacle teasing at his lips and Alec staring down at him, watching. 

Alec swallowed, his voice hoarse as he stared at Magnus. "Can I?" 

Magnus nodded, his heart pounding hard, magic sparking off his skin as the edge of the tentacle dragged over his lower lip. "I'll tell you to stop if I need it." 

Alec lifted one of the tentacles off Magnus' hand and looked down at it. "Hand signals okay?" 

Magnus eyes softened and he nodded, parting his lips, groaning as the tentacle slid into his mouth. 

"Holy shit," Alec breathed, watching as Magnus' lips stretched around the tentacle. The combination of being able to feel the wet heat of Magnus' mouth, and being able to stare was incredible. Magnus was clearly loving it too, teasing the tentacle with his tongue, sucking hard at it. "Oh fuck, Magnus..." 

Magnus met Alec's eyes and groaned, rolling his hips as a tentacle wrapped around his dick and gave him a slow squeeze, making him gasp around the one in his mouth. 

"Can I make you come just like this?" Alec asked, shifting to sit back on his heels, slowing down the tentacle around Magnus' cock, using another to grab a pillow to stuff it under Magnus' hips easily, helping to lift them. "Fuck you with them, and then fuck you myself?" 

Magnus nodded wildly, his eyes rolling back as the tentacle around his dick tightened and gave a slower, steadier squeeze. He wasn't sure that he was going to survive this, but it was going to be worth every single second. 

Alec stared down at Magnus with wide eyes. "Banish the rest of our clothes," he ordered abruptly, glad when Magnus still had enough focus to do that, grinning at all the golden skin abruptly laid out for him. Alec watched one of the tentacles slither along Magnus' stomach, this one with suckers, shuddering as they dragged along his skin, able to feel the touch even more than when he touched Magnus like that. 

"I wonder," Alec breathed, meeting Magnus' golden eyes. He grinned and had one of the suckers close over Magnus' nipple, groaning as he arched under the sensation, his entire body starting to tremble. "Fuck, look at how beautiful you are, Magnus." He had the tentacle that wasn't holding Magnus' wrists down grab him the lube from the beside drawer and pulled one away from Magnus' ass. He held it up and raised his eyebrows, glad when Magnus nodded again, rapidly. 

Magnus stared as Alec carefully made sure the tentacle going in him was lubed and tried not to hurtle towards the edge. He wanted this to last, as long as Alec was going to give him. He gave Alec a quick hand signal and gasped in a deep breath of air when the tentacle in his mouth was gone, replaced by Alec's soft lips. 

"You okay?" Alec whispered, reaching up to cup Magnus' face. "That wasn't a warning signal, but-" 

"I'm fine," Magnus panted, looking up at his frankly perfect boyfriend, who had not only taken his magical tentacles in stride, but was apparently going to fuck him until he was mindless with them. "Want to last. Cock ring." 

Alec's eyes widened and he groaned, dropping his head to Magnus' heart. "Fuck you're perfect," he breathed. 

"Trust me," Magnus exhaled hard, glad when Alec stretched over him and grabbed the suede cock ring that was one of his personal favorites. "I'm going to be saying that about you for forever." 

Alec laughed and got the cock ring into place, watching Magnus whine again, nodding. "Good, angel, Magnus, I don't know what I did to ever deserve you," he whispered, tracing the tentacle along Magnus' lips again, teasing him with it, watching him turn his head to chase it. Frozen, he held the tentacle still, just to see if Magnus would...

Magnus groaned and leaned up, just enough, sucking the tentacle between his lips again. They tasted of nothing other than the tingle of magic and he gasped as it suddenly pressed deeper, forcing him to swallow around it until he was groaning. He wanted more. He rolled his hips again, meeting Alec's eyes. He wanted to finish what they'd started. 

"Yeah, okay," Alec managed, laughing, spreading Magnus' legs wide, holding him in place. Two of the tentacles took place of his hands, holding Magnus spread wide and Magnus groaned, arching under the touch. 

"That's it," Alec breathed, watching as the tentacle he'd coated in lube, started to tease at Magnus, just faint presses into him. He focused on that, on how it felt, and the tentacle wrapped around his cock. Stroking him in counterpoint rhythm to every press in, Magnus was squirming on the sheets, rocking up and into the touch on his cock and back on the blunt press of the tentacle. 

Magnus shuddered as the tip of the tentacle pressed into him, going so slow and so gentle, because even like this, overwhelming him with so much pleasure he couldn't stand it, Alexander had to make sure to take proper care of him. He rocked his hips back impatiently, demanding more and he listened to Alec chuckle before the tentacle was sliding deeper into him. He arched back against the pillows and tightened his free hand in the sheets. 

"Fuck," Alec breathed again, dropping a hand to his cock, squeezing it to relieve just a fraction of the pressure. "Fuck, Magnus I wish you could see yourself." It was a picture that was never going to leave his mind. Magnus spread out on the bed, a tentacle in his mouth, around his cock, in his ass and two holding his legs spread wide while another pinned down one of his hands. It was most arresting (and arousing) sight he had ever seen and he wanted to take all the time he could to memorize it. 

Magnus slammed his hips hard back on the tentacle, gasping as Alec drove it into him, hitting his prostate and then teasing it with the tip of the tentacle, making him thrash on the bed. Thankfully, Alec stopped being quite so gentle and proceeded to _take_ him, forcing the tentacle in his mouth even deeper, stroking him faster, and fucking him harder. Even the tentacles around his thighs were possessive, each of the suckers leaving marks on his thighs that he knew were almost as good as bite marks from Alec's teeth. 

"I'm going to make you come, just like this," Alec promised, his eyes riveted to the picture that Magnus made. "I don't even have to do anything other than let them touch you how I'd touch you if I could." He listened to Magnus make another desperate noise as he twisted the tentacle inside him, pressing it against his prostate. "Even with the cock ring, look at you, already so desperate to come." 

Alec fought down a laugh as Magnus' eyes met his, much of the gold gone, his pupils blown wide, just a golden ring around the edges. "I never would have thought you'd like this so much. Though, maybe it's the thought that it's me being able to do all of this to you, all at once." Based on the nod that got him, he smiled and leaned down to press a kiss to Magnus' heart. 

"I love you," he whispered, trailing his hands down and over Magnus' chest, down his abdomen. "I love that you're letting me do this, that you're trusting me to take care of you, to stop if you need..." Alec pulled the tentacle in Magnus' mouth back just a fraction, just to savor the sight of him surging up to take it deep into his mouth again. "I'm going to take such good care of you, Magnus," he promised, breathing out hard. 

Magnus nodded, tears gathering at the corner of his eyes as Alec forced the tentacle into his mouth deep again. He sucked on it desperately, bobbing his head around it, thrusting up into the tentacle jerking him off, and then back down onto the tentacle fucking him. It was overwhelming in the best way, and all of it, all of it overshadowed by the awed way Alexander watched him as he did. 

"I could watch you do this for hours," Alec breathed, reaching out to tease his fingertip along the tip of Magnus' cock. It was tempting to do exactly that, but he also had too much fun he wanted to have with this, and if Magnus got too fucked out, they'd spend much of the time he had the tentacles sleeping. "But why don't you show me how much you want to come, and I'll let you?" 

Magnus whined, nodding his head around the tentacle again, straining against the bed as the tentacle in him sped up, pressing in deeper, fucking into him with obscene noises that echoed into the room. Alec's fingers were at the base of his cock shortly after and he gasped as the cock ring fell away and down to the bed. When Alec met his eyes again, Magnus fought to hold himself back, even as everything got faster and more intense, leaving him trembling and shaking with the effort not to come. 

"So beautiful," Alec breathed, slowly trailing a hand down Magnus' side. "Fuck, Magnus, you're so beautiful, and you're all mine," he promised, watching Magnus give another keening whine at the statement. "Let me see you come, let me see how good they're making you feel." 

With that, Alec pulled back, his eyes devouring the way Magnus closed his own eyes, his body thrashing and thrusting into every touch of the tentacles. He was mesmerizing, his hips rolling and demanding more with every second until it was easy to see the way his thighs were tensing and every motion was frantic, chasing the edge that he was so desperate to fly over. 

"Come on, Magnus. Come for me," Alec whispered, licking his lips. 

Magnus was overwhelmed, but he could never deny such a gentle order from his Alexander. With a shout around the tentacle in his mouth, Magnus came, his whole body shaking with the force of his orgasm, barely managing to contain the magic rippling under his skin so he didn't do some damage to the tentacles that were a part of Alec. Panting, he sucked in deep breaths of air as the tentacle slipped out of his mouth and from inside him, Magnus reached out, grabbing for Alec, and pulling him in close. 

"I'm here," Alec breathed against Magnus' lips, kissing him, letting Magnus pull him closer until he didn't know where one of them ended and the other began. He smiled and reached up, combing his fingers through Magnus' wild hair, grinning at his dazed eyes. "You okay?" he whispered. His tentacles were curled around the both of them, satisfied for now and he couldn't help grinning. 

"Alexander," Magnus huffed out a laugh, his voice hoarse as he forced one eye open. "If you don't have any idea of _precisely_ how good that was for me, I'm going to accuse you of being blind." 

Alec laughed a little and stole another kiss, humming into Magnus' lips. "I know, but you know that's not what I meant, Magnus." 

Magnus hummed and stretched. His body felt sore, but not overused. It had been perfect. He grinned and reached up to comb his fingers through Alec's hair. "Perfect. Rather like you, my dear Alexander." 

Alec huffed out a laugh and sat back on his heels again, taking in the picture of Magnus, still sated and spread out on the bed. "You know, they're pretty handy, I have to say." 

"Alexander," Magnus groaned. "You've just given me a mind-blowing orgasm, please take pity on me and give me at least a few minutes to enjoy it before you start making horrible sex jokes." 

Alec laughed, snickering as he stretched out beside Magnus, reaching out to touch his arm gently, even as the warlock waved a finger to clean up the mess that they'd made. "You like it when I make horrible sex jokes, because I never would have made them when we first started dating." 

"Of course I do," Magnus said with a huff, giving Alec's arm a smack. "Doesn't mean I want you to ruin a perfectly good afterglow." 

Alec smiled and leaned in to press a kiss to Magnus' heart. "I love you," he whispered. 

Magnus smiled and reached out to wrap an arm around Alec. "I love you too, and as soon as I can feel my legs again, I'm going to make sure to thank you, _quite_ thoroughly, for how good that was." 

Alec grinned. "I'm looking forward to it. What are you planning, hm?" 

Magnus thought about that and tilted his head. "I'm thinking that I might ride you. What do you think about that?" 

Alec shuddered and gasped, nodding. "Y-yeah, fuck, please." 

"Good," Magnus said with a hum, stretching out on the bed, even as one of the tentacles started to curl over his ass. He looked down at it and snickered. "And that'll give you the added benefit of being able to touch me with them as much as you want." 

"Magnus," Alec growled, shifting his hips impatiently. "Thought you wanted to enjoy your afterglow." 

"Oh I do," Magnus agreed. "I just happen to like riling you up almost as much as I like enjoying my afterglow." 

"Don't make me pin you to the bed again," Alec growled, watching Magnus shiver and grin. 

Magnus hummed and looked appraisingly at the tentacles. "Do you think you could make them fuck you, too?" 

Alec blinked and groaned, a shiver running through him, another blurt of precome escaping his cock. "Uh, I could try? Why, what are you thinking?" 

Magnus licked his lips, looking up at Alexander. "Making plans for our next round after I finish this one." 

Alec laughed and shook his head, pushing himself upright. "Does that mean we're going to finish this one now?" 

Magnus pushed himself upright with another pleased stretch and hummed, gesturing for Alec to take his turn in the pile of pillows. "Oh yes. After all, you've gotten me all nice and stretched for you, so we may as well take advantage of it, shouldn't we?" 

"Yeah," Alec managed as he settled back into the pile of pillows and stretched out, dropping one tentacle to his cock, wrapping it around himself to stroke, slow and teasingly. He gasped and tilted his head back. “See why you liked it so much,” he managed, licking his lips. 

"Tease," Magnus growled, watching as Alec lifted his eyes to stare at him with a smug grin. 

Alec blew Magnus a kiss and smirked, watching as his boyfriend straddled him. With another snap, he could feel Magnus' hand wrapped around him along with the tentacle, making him gasp. 

"I think," Magnus purred, licking his lips. "That next time, when I fuck you, Alexander, we'll have one around your cock, and one in me. What do you think?" 

Alec shuddered and gasped, dropping his hands to clench the sheets as Magnus got him into position and then slowly started to lower himself. "Magnus, come on," he growled, trying to roll his hips up, only to find himself pinned in place by his own tentacles. 

Magnus smirked and sank down another inch, savoring the stretch and different feel of Alec in him. His mouth dropped open a fraction and he lifted himself up a bit before slamming the rest of the way down with a loud groan. "Looks like they want to help you behave for me," Magnus teased, shivering as two tentacles reached out to wrap around his hips, clearly ready to help him move. "So kind too," he teased. 

"You're going to kill me," Alec said, clenching his teeth, trying to hold back as Magnus teasingly rocked his hips, grinding down into his lap, not lifting himself just yet, only teasing him. 

"Come now, Alexander. Where's that famous shadowhunter control?" Magnus teased, licking his lips as he lifted himself a fraction before sliding down. He groaned, humming happily. "I have to admit, as much as I enjoyed you fucking me with them, I am still very partial to this," he teased, lifting himself all of the way off Alec's cock, just to watch his boyfriend twitch in impatience below him before he slammed back down, the tentacles pulling him into the thrust. 

"Magnus!" Alec shouted, his whole body shaking as Magnus started to ride him in earnest. His hands were tangled in the sheets and all he could do was hold on as he watched his tentacles possessively stroke over Magnus' body, teasing his nipples, holding onto his hips and helping him to balance. "Fuck, you're so beautiful," he breathed. 

Magnus hummed and rolled his hips again as he was seated fully in Alec's lap again, savoring the loud groan that got him. "If you could see what I do, I'm sure that you'd disagree," he teased, staring at his boyfriend spread out on golden sheets. "On the other hand, the tentacles do lend to helping that I suppose." 

Alec bit down on his lip and growled, trying to thrust up and into Magnus' next grind down, but the tentacles kept him pinned, making him whine. "Fuck, Magnus please, go a little bit faster?" he begged. 

"I'll think about it," Magnus said, even as he started to increase the pace, glad for the tentacles that were making this so much easier on his thighs. If he loved the suckers digging into his hips just like Alec's fingerprints did, well, he could tell Alec that later. Maybe he'd get matching fingerprints. He dropped a hand to his cock, giving himself a teasing squeeze. He was still just a bit too sensitive, but the knife edge of pain felt good and he groaned, sliding down on Alexander's cock as he stroked himself. 

He couldn't look away from the sight Magnus made, riding him, clenching down on him with every thrust and grind of his hips, tentacles possessively holding onto him and keeping him steady, and a hand around his cock. Alec licked his lips and groaned, before he realized something and his eyes widened. Once he'd had the thought, one of the two tentacles that had been teasingly running across their skin was poking at his lips. 

A punched out groan escaped Magnus as he watched Alec suck the tip of a tentacle into his mouth. The sight was arresting and Magnus stared, frozen, until he started riding Alec again in earnest, grinding his hips down with rough and hard snaps. "Fuck, Alexander, look at you..." Magnus breathed, watching those pink lips stretch around the iridescent blue of the tentacle. It was almost as obscene as they looked stretched around his cock. He was almost glad for the tentacle that took over stroking his dick so he could focus all of his attention on how good Alexander looked and felt. 

"I've never seen anything so beautiful," Magnus managed to get out, his voice hoarse as he slammed his hips down again, whining as he found the perfect angle that he wanted to keep Alec at. His tentacles must have realized it too, because they tightened around his hips and helped him to keep hitting that angle again and again until he was shaking with the effort of holding back. 

"Alec," he managed, tossing his head to get some of his hair out of his face. "Gonna come for me, darling?" He clenched down around his shadowhunter again and felt Alec's whole body buck against the hold of his own tentacles, a desperate whine escaping from around the one in his mouth. 

Alec was going to shake apart. Everything was too much, he could feel Magnus’ skin, and his own mouth, and how good Magnus' cock felt inside the circle of his tentacle and how tight and hot he was as he rode him. He nodded, desperate to have Magnus give him permission to finish letting go, he needed it, unable to keep himself from falling over the edge any longer. 

"Just a little longer," Magnus coaxed, watching Alec whine and try to nod around the tentacle. He kept up the slow and deep rolls of his hips, grinding down on that perfect angle, gasping when a sucker from one of the tentacles was pressed to the tip of his cock, the additional suction driving him closer and closer to the edge. "Want you to come with me," he panted, feeling Alec strain to try and hold himself back. 

It was all too good and too much, Magnus above him, looking so hot, and sexy and beautiful and all Alec wanted to do was keep him forever. Keep him right here, like this, his, all properly claimed and _his._ He bit down another gasp as Magnus started to move more frantically, his tentacles straining to help Magnus reach that edge he was reaching for. 

"That's it, that's it, fuck!" Magnus swore, clenching down on Alec hard, making a mess of Alec's tentacle and his chest, his thighs shaking with the effort of holding himself up as he ground down against Alec. He couldn't look away as he watched his boyfriend moan around the tentacle again as he came, bucking his hips up hard and deep. 

Alec's orgasm almost caught him by surprise as Magnus tipped over the edge and brought them both over together, shuddering and shaking until they fell together in a sweaty pile of limbs and....tentacles. 

Magnus broke out into giggles and gave one of the tentacles a small shove, making it make room for him to cuddle against Alec's chest. "You okay darling?" he asked, cuddling up to him. One of the tentacles wrapped around his waist, holding him in close and he grinned. “Oh god, you’re actually going to have octopus limbs now.” 

Alec burst into laughter, his chest heaving a little as he did, shifting so he could lay on his side, two more of the tentacles possessively curling around Magnus. He leaned in and kissed Magnus, soft and gentle, pressing their foreheads together. “Guessing you don’t mind all that much.” 

Magnus hummed into the kiss and smiled. “I’d say it’s a very good thing that we’re going to spend the next thirty six hours in bed.” 

Alec gave a contemplative hum and nuzzled into Magnus’ neck with a sigh, glad when Magnus’ arms came around his shoulders. He closed his and started to doze, when one of Magnus’ fingers stroked along the patch of skin his tentacles were coming from and his whole body shuddered, his eyes flying open as he groaned. 

Magnus paused, opening his eyes and raising his eyebrows, watching Alexander blush like he hadn’t since they had finally started sleeping together. Slowly, he pressed his fingers to the base of the tentacle again and watched Alec’s whole body tremble, a panted gasp escaping him. 

“F-fuck, Magnus,” Alec whined. 

Magnus’ eyes lit up. “Well, well,” he drawled, flipping him over so Alexander was pinned to the bed beneath him, his entire back exposed. “We’ll just have to see about this…” he purred, dragging his fingers down the expanse of Alec’s back, pressing in at the base of each tentacle. 

Alec shuddered again, gripping the bedsheets tight, his dick already half hard and getting harder. “You’re going to kill me,” he rasped. 

“Oh no,” Magnus purred, leaning in close to nuzzle Alexander’s neck. “But…” he grinned and lifted his fingers to the tip of Alec’s spine, and dragged them down in a slow, steady motion, feeling Alec gasp and shudder beneath him. “I am going to see if you can come from just this.” 

Alec moaned into the pillows, arching into the touch. He couldn’t wait to find out either.

**Author's Note:**

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